;Compiler V3.5.2.7
; With Filler[50] enabled. fails    => Testing,278,278,213,164,127,100,79,64,52,44,37,32,278,278,278,278
; With Filler[50] disabled. correct => Testing,278,278,213,164,127,100,79,64,52,44,37,32,94,140,174,200

  Device = 16F916 ;8K Words,352 Ram, 256 EEPROM, 24IO, 8*10bitADC, LCD 16Seg, Comparator, 44pin TQFP
  @ CONFIG_REQ = 0 ; Override Compiler's configuration settings
  Asm-
    __Config  0x3094 ;FOSC_INTOSCIO & WDTE_OFF & PWRTE_OFF & MCLRE_OFF & CP_ON & CPD_OFF & BOREN_OFF & IESO_OFF & FCMEN_OFF & DEBUG_OFF 
  Endasm-
  Declare Xtal = 4
  Declare Keep_Hex_File    = On  
  Declare Rsout_Pin PORTA.4     ;Debug pin
  Declare Rsout_Mode 0          ;Connect to logic I/F lead
  Declare Serial_Baud 9600      
  Declare Rsout_Pace 0

'  Dim Filler[50] As Word       ;Enable this line to make program fail
  Dim DigFilterIn     As Word     ;Current value. Input value to [all] filter(s)
  Dim DigFilDiff      As Word     ;Deviation of current value from smothed one
  Dim DigFilDiff_High As DigFilDiff.HighByte  ;Point to high byte of DigFilDiff Word
  Dim DigFilterSign   As Bit      ;Sign of change 1=negative [Sign bit for Word value]
  Dim DigFilterOut    As Word     ;Smothed output from digital filter
  Dim DigFilterAcc    As Word     ;Accumulator for Filter

Boot:                     ;Power on reset
  OSCCON = %01100000      ;4Mhz  
  PORTA  = %00010000 
  TRISA  = %11101111   
  CMCON0 = %00000111     ; Make digital I/O, Comparator mode off, low power
  LCDCON = %00000000    ;Turn off "default" LCD functions for PortC PIC Hardware
  GoTo Main

DigFil:
  DigFilDiff = DigFilterIn << 4    ;Calc difference from current smothed value
  DigFilDiff = DigFilDiff - DigFilterAcc   ;Calc difference from current smothed value
  DigFilterSign = DigFilDiff_High.7   ;Get Sign of the diference (Topbit of word is signbit)
  DigFilDiff = Abs DigFilDiff         ;Magnitude the difference
  DigFilDiff = DigFilDiff + 3    ;1/4 of the difference, or 1 or 0 (Dither adjust)
  DigFilDiff = DigFilDiff >> 2    ;1/4 of the difference, or 1 or 0 (Dither adjust)
  If DigFilterSign = 0 Then           ;+ve change
    DigFilterAcc = DigFilterAcc + DigFilDiff    ;Update smothed value
  Else                                ;-Ve
    DigFilterAcc = DigFilterAcc - DigFilDiff    ;Update smothed value
  EndIf
  DigFilterOut = DigFilterAcc >> 4   ;/16 Generate new smoothed output value from filter 
  RSOut ",",Dec DigFilterOut
  Return

Init_Filter: ;Preload filter with current measuremet
  DigFilterOut = DigFilterIn       ;Same as input value on init
  DigFilterAcc = DigFilterIn << 4  ;x16 Initialise accumulator starting value
  Return

Main:
  RSOut "\r\nTesting"
  DigFilterIn =278
  GoSub Init_Filter

DataSet:
  DigFilterIn = 278 : GoSub DigFil
  DigFilterIn = 278 : GoSub DigFil
  ;
  DigFilterIn = 18 : GoSub DigFil
  DigFilterIn = 18 : GoSub DigFil
  DigFilterIn = 18 : GoSub DigFil
  DigFilterIn = 18 : GoSub DigFil
  DigFilterIn = 18 : GoSub DigFil
  DigFilterIn = 18 : GoSub DigFil
  DigFilterIn = 18 : GoSub DigFil
  DigFilterIn = 18 : GoSub DigFil
  DigFilterIn = 18 : GoSub DigFil
  DigFilterIn = 18 : GoSub DigFil
  ;
  DigFilterIn = 278 : GoSub DigFil
  DigFilterIn = 278 : GoSub DigFil
  DigFilterIn = 278 : GoSub DigFil
  DigFilterIn = 278 : GoSub DigFil
  ;                               
  While 1=1
    Nop
  Wend
  End